^^
Here is some food for thought.
My old divers knife was about 6 inches long, probably longer with the sheath. Could come in handy once in a blue moon. The only problem is it is another thing strapped to you. i prefer to use my line knife which is in a concealed pocket in my harness. Less bulk when kiting certainly is better.
The advantage I see is that if i needed to use a knife in a hurry, the divers knife would probably get used in cutting me loose, as i strap it on each time i kite, and it would be in the front of my mind, as it is highly visible highly accessible, and in my memory bank whilst kiting.
If i was relying on my line knife, i would probaly forget that i had it because it is in the pocket on my harness. I forget that it is there, as i put my harness on dont even think about the knife.
The moral of the story is if you have a line knife. Periodically check it, make sure its there, make sure its not rusted. And go through all your emergency scenarios in your head frequently, so all avenues of safety are included. I.e Quick release, knife, location, water rescue. Etc.
KR